Molecular methodology has been used extensively in recent years to investigate patterns of genetic diversity in natural populations. For example, the polymerase chain reaction permits the specific amplification of DNA regions that have been identified from research in different taxa. By this methodology we amplify viral, immune system loci, oncogenes, mitochondrial DNA, and other genomic regions based on homology with published sequences from laboratory species. Investigating genetic diversity in these genomic components from free-ranging nondomestic species permits a comparative analysis which can tell us a great deal about evolutionary divergence and functional adaptation. Some of the more recent advances include: (1) discovery of widespread seroprevalence with 25 species of Felidae for feline immunodeficiency virus, (2) discovery of highly mutable repeat sequences in the carnivore mitochondrial DNA control region that produce massive heteroplasmy in a manner reminiscent of quasi species expansion, (3) the severe infestation of genetically depauperate Asiatic lions with pathogenic papillomavirus, (4) solving the phylogenetic puzzle about the red panda's origins by aligning the species with Procyonidae, and (5) further molecular resolution of Felidae evolution among South American small cats and pantherine species.